This invention relates to a method of matching between images, between graphs, and between an image and a graph, and more particularly, to a method of extracting inherent characteristics of an image and a graph from neighboring regions to perform matching between the image and the graph.
There are increasing demands on integration of data extracted from multiple sources along with development of computer technologies. Image matching is one of most important technologies for data integration. A large number of literatures are also available, such as Barbara Zitova and Jan Flusser, Image registration methods: a survey, Image and Vision Computing 21 (2003), pp. 977-1000, October 2003. The conventional methods of image matching are almost based on deriving correspondence among feature points which are firstly extracted as corner points, cross points, edges, and the like from both image pairs. Intersections and roads are used as feature points to be extracted from a map. Scale invariant feature transform (SIFT), which handles a local feature value, is popular and commonly known as an exemplary method for finding invariant feature points with high performance, as described in, for example, U.S. Pat. No. 6,711,293.
The above-mentioned conventional technologies have a premise that feature points must exist in both images, and therefore require the images with similar modules, which means that images may be taken from different sensors with different imaging conditions such as angles, illumination, and occlusion, but pixels of the images of the same object need to represent similar physical attributes, for example, two pictures of the same object taken from different locations, or a satellite image and an aerial photo of the same place.
However, for different types of data, such as an image and a map, or a visible image and a thermal image, the feature points extracted therefrom represent totally different physical attributes, which are not feasible to consider the correspondence thereamong. Therefore, the conventional image matching technologies cannot directly be applied to matching between an image and a graph, between images with different modules, and between graphs with different modules.
The conventional image matching methods cannot directly be applied to matching between an image and a map because the feature points extracted from the image do not necessarily correspond to the nodes of the map. The conventional matching between an image and a map is performed through selection of ground control points (GCPs) from both the image and the map, which is equivalent to setting up of corresponding feature points, and no knowledge of the image and the map are directly utilized. Accordingly, it is difficult to automate the matching between an image and a map.
In view of the above, this invention has an object to automatically obtain a feature value to be used for matching between an image and a graph (or between images or between graphs) with different attributes.
A representative aspect of this invention is as follows. That is, there is provided a computer system for matching between images, between graphs, and between an image and a graph, the computer system comprising: a processing unit for executing a program; a storage unit for storing the program executed by the processing unit; an input unit for receiving at least two of the image and the graph to be matched; a data recording unit for storing, in a storage device, the received image and the received graph; a feature pattern generating unit for generating a set of feature patterns of the image and the graph by reading the received image and the received graph from the storage device, segmenting each of the read image and the read graph into a plurality of regions centered on each of a plurality of sample points, and determining characteristics of the plurality of regions obtained through the segmentation; a correspondence computing unit for computing correspondence between the image and the graph to be matched by comparing the generated feature patterns; a transform unit for transforming a coordinate system of at least one of the image and the graph to be matched based on the computed correspondence; and a combination unit for combining the image and the graph that have been subjected to the transform of the coordinate system.
According to the representative embodiment of this invention, the automatic, precise matching between the image and the graph can be realized while saving time therefor.